The present invention relates to a load voltage control device which controls a voltage supplied to a load, and more specifically to a load voltage control device which controls a voltage supplied to a load via a cable, an electronic endoscope and an electronic endoscope system.
Conventionally, electronic endoscopes capable of observing and capturing a target portion by inserting a long slender insertion unit into a body cavity of a patient have been widely used. In an electronic endoscope of this type, an image pickup device (e.g., a CCD image sensor or a CMOS image sensor) for capturing the inside of a body cavity is disposed in a tip portion of the insertion unit. Supplying of a power supply voltage to the image pickup device is performed via a long cable from a power supply circuit disposed in a proximal end portion of the electronic endoscope (i.e., a connection part to a video processor) or disposed in a video processor. In this case, a voltage drop by the cable may affect image capturing and cannot be neglected. Therefore, a designer may consider configuring a power supply circuit to generate a power supply voltage to which a voltage corresponding to the voltage drop is added in advance, and to supply the power supply voltage to an image pickup device. However, the length and specifications (e.g., electric resistance) of a cable connecting the power supply circuit with the tip portion of the electronic endoscope varies depending on the type of the electronic endoscope. Further, the loss caused by the cable also varies depending on the type of the electronic endoscope.
Japanese Patent Provisional Publication No. 2009-106442A (hereafter, referred to as patent document 1) suggests technology for solving the above described problem. In an endoscope described in patent document 1, a correction value corresponding to a property of a cable is stored in advance in a memory, and a signal transmitted to an image pickup device is corrected (e.g., amplification) based on the correction value.